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Connecting a microphone to PCM3168A

Jacob Gontmacher
Prodigy 120 points
Other Parts Discussed in Thread: PCM3168A, OPA4134, PCM3168A-Q1, OPA134, PCM3168

Hi,

 

I'm thinking about connecting a non amplified microphone signal to PCM3168a.
Since this coded requires differential signal, I'm using OPA134 (OPA4134 integrated circuit) as suggested by Figure 61 on page 57 on http://www.ti.com/lit/gpn/pcm3168a-q1.

My question is: is it a smart move?
The circuit on figure 61 gives me 0.5db gain to already non-amplified signal. Will it be high enough for PCM3168a to receive it well?

Thanks,

Jacob.

  • 0
    TI__Guru**** 189399 points

    Jacob,

    You are on the right path. I think you're going to need more than 0.5 dB of gain, though. Your mic signal is going to be so low, it's going to be in the noise floor.

    -d2

  • 0 in reply to Don Dapkus
    Prodigy 120 points

    Hello Don,

    Thanks for the reply.
    What would you recommend to do?

    Should I amplify the mic. signal prior to making it differential?
    Can you suggest a good Ti component for that?

     

    Jacob

  • 0 in reply to Jacob Gontmacher
    Guru 21975 points

    Jacob,

    Here is a schematic that may serve as a starting point. Refinements will depend on your application details. What type of microphone are you using? What is the sound source?

    The gain is set by R3/R4 and the lower amp just inverts for differential output. It may be possible to eliminate C2, once the gain is established. The op amp selection depends on the details of the application such as microphone type and signal level. I'll be happy to offer further help after you consider this approach.

    Regards, Bruce.

    Regards, Bruce

  • 0 in reply to Bruce Trump
    Prodigy 120 points

    Hey Bruce,

    Thank you very much for this input.
    Right now I have the simplest microphones you can find in a local components store, they are the source.
    I still don't know if those mics will be my final choice because I'm looking into buying an amplified differential signal microphones
    but if I'll stick to the simple ones I will prefer your schematics over those suggested in PCM3168 because your schematics offer an adjustable gain control.

    Jacob.